基于全局排序模式同步的多通道脑电同步特性分析

脑电同步是脑功能区域整合的重要表现。基于时间序列的排序模式,提出一种简单易行的多通道脑电信号同步分析方法--全局排序模式同步(GMS)。仿真分析显示,该算比基于加权排序互信息的全局同步因子对弱耦合的检测更为灵敏。对26例遗忘型轻度认知障碍和20例认知功能正常的2型糖尿病患者闭眼静息态的脑电信号,采用基于小波增强的独立分量分析算法进行预处理,将32路脑电信号分为前额、中央区、顶区、枕区、左颞和右颞6个区域进行全局同步分析,并利用独立样本t检验对两组被试之间的人口学特征、神经心理学检查和同步值进行统计分析,利用皮尔森线性相关分析研究各区域同步值和认知功能之间的关系。结果显示,糖尿病轻度认知障碍患者与正常对照组相比,各脑区的全局排序模式同步值均减小,尤其是中央区(P<0.01)、顶区(P<0.05)和枕区(P<0.05)有显著性的降低,且前额(r=0.298,P=0.045)、中央区(r=0.327,P=0.026)、顶区(r=0.32,P=0.03)的全局排序模式同步值均与MOCA得分有显著的正相关性,表明GMS是与认知功能下降相关的脑电特征。     

体感电刺激诱发事件相关电位的研究

目的对视觉、听觉、体感3种不同模态下靶刺激诱发的事件相关电位(ERP)进行比较研究,探讨体感电刺激作为脑机接口(BCI)一种新的信号诱发模式的可能性,为基于体感ERP的BCI研究提供理论依据。方法选择17例视力或矫正视力正常、听力正常、躯体感觉正常且无任何大脑病史的被试者,其中男性8例,女性9例;年龄20~26岁,平均年龄22.6岁;均为右利手。分别记录17例健康的被试者在视觉、听觉、体感单通道靶刺激下诱发的脑电图;对3类靶刺激下ERP的时域参数(幅值、潜伏期)、行为学数据(反应时间、错误率)、脑源定位进行比较分析。结果 3类靶刺激模式下的ERP波形具有相似性,体感电刺激诱发的ERP幅值与视觉、听觉靶刺激相比无显著性差异;体感电刺激诱发ERP的峰值潜伏期显著长于视觉靶刺激;体感电刺激的反应时间显著长于视觉靶刺激,错误率也高于视觉、听觉靶刺激;体感电刺激诱发ERP的脑内源与视觉靶刺激相比具有相似性。结论相比于视觉、听觉靶刺激,大脑对于体感电刺激的探测难度高,敏感程度低;但从ERP的波形和幅值上看,体感电刺激可以诱发出稳定的、可被检测到的ERP波形,完全有可能应用于BCI系统作为一种新的ERP诱发模式。     

低频重复经颅磁刺激刺激初级运动皮层对大脑功能连接影响的研究

重复经颅磁刺激(rTMS)能对刺激脑区及与其相连接的远端脑区产生影响。本文将从大脑功能连接、脑区之间相互协调工作状态改变的角度,研究低频rTMS刺激脑初级运动皮层对大脑的影响作用。募集了10名健康受试者,采用1 Hz rTMS刺激脑初级运动皮层20 min,采集刺激前后1 min闭目静息状态下的脑电(EEG)数据。对EEG进行相位同步分析,建立脑功能网络,并计算脑功能网络特征参数。最后使用符号秩和检验进行统计学分析。结果表明,低频rTMS刺激使大脑alpha频段全局相位同步指数显著降低(P0.05)。两两脑区分析表现为刺激侧的运动皮层与额叶皮层和顶叶皮层、非刺激侧顶叶皮层与双侧额叶皮层之间alpha频段相位同步显著降低。alpha频段脑功能网络的平均度、全局效率降低(P0.05),平均最短路径长度显著增加(P0.05)。表明低频rTMS使脑功能网络的信息传输变慢,传输效率变低。本文从大脑功能连接性的角度上证明了低频rTMS对大脑活动的抑制作用,说明低频rTMS能够对刺激脑区及与刺激脑区相连接的远端脑区产生影响。本研究有望为低频rTMS应用于临床疾病的治疗提供一定的指导。     

视、听感知下模拟驾驶行为的脑电实验比较研究

目的 研究基于视觉、听觉以及视听融合感知的刺激源对脑电(EEG)识别率的影响。方法试验分别从视觉、听觉和视听融合3种情况提供与交通环境相关的刺激源,在不同刺激源的提示下,受试者利用左右手想象运动对车辆进行启动和制动控制,并对采集的脑电数据进行特征提取和分类处理,得到与想象运动相关的C3、C4导联上的特征信号和分类结果。...     

视觉刺激下基于“是-否”状态的脑电信号分类研究

目的为了探究脑机接口中脑电信号与判断认知心理活动之间的识别问题,本文在视觉刺激诱发实验设计中采用文字和图片结合的方式进行脑电分类研究以期提高识别率。方法通过设计视觉刺激诱发判断认知脑电实验采集到15名受试者在"是"或"否"状态下的脑电信号,经过预处理和事件相关扰动(event-related spectral dynamics,ERSP)特征分析,运用经验模式分解(empirical mode decomposition,EMD)优化共空间模式(common spatial pattern,CSP)的特征提取算法进行分类识别。首先,利用EMD对预处理后的脑电信号进行有效的固有模态函数(intrinsic mode function,IMF)频段筛选;其次,使用CSP滤波器进行滤波提取特征向量;最后,使用支持向量机(support vector machine,SVM)进行分类识别,并对测试组进行检验。结果经过EMD-CSP优化滤波后进行SVM分类正确率可达8897%,相比单独利用CSP进行特征提取下的SVM分类结果提高了约5%。结论 EMD-CSP优化滤波方法对判断认知脑电识别的可行性和有效性,为进一步开发脑机接口应用产品提供认知参考依据。     

做梦的认知神经理论及机制

做梦的认知神经理论可以从梦的形成和梦的功能两种角度来看。做梦的认知神经机制研究集中于脑解剖研究和脑成像研究。脑解剖研究关注梦的形成,脑成像研究关注梦的认知。已有的研究表明,做梦是特定脑区(颞-顶-枕联合区、前额叶和边缘系统)的功能,这些脑区的激活可能解释了做梦时感知觉、意识和情绪方面的认知特点。未来的研究方法上可使用新兴的同步脑电和功能磁共振成像技术、发展跨文化的梦的研究等。     

老年人轻度认知障碍部分定向相干脑网络分析

近年的研究表明,轻度认知障碍(MCI)患者的认知加工呈现脑连通性缺失特征,但各脑区间如何影响,因果特性不明。本研究的目的在于分析MCI患者在认知任务下的有向脑网络特征。采集了30位老人在信息冲突颜色认知作业下的头皮脑电,包括21位正常人和9位MCI患者。选取刺激呈现后的脑电计算其部分定向相干值,依此构建脑网络,并着重分析了不同脑区的入度差异。研究发现：在beta段,MCI患者右前额区信息流入缺失,左中央区的信息流入异常增强;在患者组和正常组中前脑区的入度要远高于后脑区;正常人在匹配和不匹配刺激下右脑区的入度要高于左脑区;但是在患者组中左右脑区的入度却没有明显差别。在特定阈值下：正常人在匹配刺激下左脑区（阈值0.14）的入度要低于MCI患者（F=3.780,P=0.040）;正常人在不匹配刺激下左脑区（阈值0.26）的入度要低于MCI患者（F=3.780,P=0.040）;正常人在匹配刺激下右脑区（阈值0.18）的入度要高于MCI患者（F=3.941,P=0.021）。文章从入度为脑网络特征验证了MCI患者在颜色认知任务下右脑的功能缺损。     

基于听觉感知任务下的脑电驾驶实验研究

探索在听觉感知的交通信息提示下,进行左右手想象运动对车辆进行辅助控制的脑电特征。受试者在模拟的鸣笛和刹车环境中进行左右手想象运动控制车辆的前进和停止,对采集的脑电进行了基于公共空间模式CSP和线性回归算法的特征提取及分类,识别率达96.67%。结果显示:在与左右手想象运动相关的电极C3、C4上,均表现出右手想象任务引起的脑电幅值高于左手任务,最大幅值差可达120μV。结论:与传统的在视觉感知下进行的左右手想象任务相比,听觉感知任务下的脑电存在着很大优势:(1)两种想象任务引起的脑电幅值差异更大,更有利于信号的提取;(2)脑电的获取可以取代传统的双电极采集方式,选用C3或C4单电极实现。     

基于EEG脑网络的视觉呈现速度对工作记忆影响的研究

随着生活节奏加快，倍速播放在学习过程中被广泛应用，对学习认知活动的影响也逐渐被学者所关注。为探究记忆任务的视觉呈现速度对工作记忆的影响及其机理，本研究从EEG脑网络的视角展开研究。设计了快慢两种呈现速度下的实验范式，并对18名被试的脑电数据进行采集，计算各频段的功率谱并选择具有显著性差异(P<0.05)的频段进行分析。采用格兰杰因果的方法计算不同频段脑区之间的因果关系并构建加权因效性脑网络，分析网络的入度、出度和聚类系数这3种网络特征，并使用支持向量机对快慢状态下的脑网络进行分类。结果显示，在快速视觉呈现状态下，脑网络出入度增加，节点聚类系数进一步加强，且具有显著差异节点主要分布于额叶、顶叶和枕叶，显著高于慢速视觉呈现状态(P<0.05),以各频段入度、出度、聚类系数作为特征对快慢状态下的脑网络进行分类，分类准确率分别最高可达90.96%、90.29%、86.53%。本研究表明，随着视觉呈现速度加快，视觉加工进一步激活，被试的工作记忆意识活动逐渐增强，大脑左半球对语言、推理等认知活动的主导作用也在不断加强。本研究为探究播放速度对学习认知活动的影响提供了新的研究思路，也为学习...     

视差深度多线索认知研究

认知过程研究的目的是探索人的智力这个令人印象深刻和能够不断发展的能力是如何发生和被调控的。我们长期以来一直通过立体视觉研究这个核心问题。本文根据科研实验要求建立了一套多导视觉诱发脑电(VEP)信号采集处理系统，用于立体视觉认知过程脑电(EEG)信号的提取和分析处理。我们对视差深度相关的视觉诱发电位特征发放进行了标识，初步确定了体视视差深度信息处理是在高级视皮层功能区完成的，立体视觉深度相关脑诱发电位提取的实验结果与其它研究结果基本一致。我们认为立体视觉深度认知过程是一个动态多信息处理过程，皮层高级功能区深度认知是生物反馈作用于体视信息处理全过程的结果，这是我们在心理物理研究过程中提出一个重要假设，本文提供了相应的实验证实。     

Visually evoked phase synchronization changes of alpha rhythm in migraine: correlations with clinical features.

OBJECTIVE: This study aimed to compute phase synchronization of the alpha band from a multichannel electroencephalogram (EEG) recorded under repetitive flash stimulation from migraine patients without aura. This allowed examination of ongoing EEG activity during visual stimulation in the pain-free phase of migraine. METHODS: Flash stimuli at frequencies of 3, 6, 9, 12, 15, 18, 21, 24, and 27 Hz were delivered to 15 migraine patients without aura and 15 controls, with the EEG recorded from 18 scalp electrodes, referred to the linked earlobes. The EEG signals were filtered in the alpha (7.5-13 Hz) band. For all stimulus frequencies that we evaluated, the phase synchronization index was based on the Hilbert transformation. RESULTS: Phase synchronization separated the patients and controls for the 9, 24 and 27 Hz stimulus frequencies; hyper phase synchronization was observed in patients, whereas healthy subjects were characterized by a reduced phase synchronization. These differences were found in all regions of the scalp. CONCLUSIONS: During migraine, the brain synchronizes to the idling rhythm of the visual areas under certain photic stimulations; in normal subjects however, brain regions involved in the processing of sensory information demonstrate desynchronized activity. Hypersynchronization of the alpha rhythm may suggest a state of cortical hypoexcitability during the interictal phase of migraine. SIGNIFICANCE: The employment of non-linear EEG analysis may identify subtle functional changes in the migraine brain.     

Visual presentation of hand image modulates visuo–tactile temporal order judgment

Perceptual systems can distinguish among a variety of inputs in the temporal domain, including even different sensory inputs. This process has been investigated mainly by using a temporal task (temporal order judgment: TOJ). For example, studies have reported estimated critical limits (just noticeable difference: JND) of the TOJ between a visual stimulus and a tactile stimulus (visuo–tactile TOJ, e.g., flashes and vibrations) fell within a certain temporal range. Recent studies have also suggested that the visual presentation of a hand image could modulate visuo–tactile integrations in the temporal domain, but these studies did not thoroughly examine such effects by using temporal tasks. Here, we investigated the effect of visual presentation of a hand image on visuo–tactile TOJ. In our experiments, a visual stimulus was presented on the index finger of a hand image and a tactile stimulus was presented on the index finger of a participant’s hand. We found that the JND of visuo–tactile TOJ became larger when a forward hand image was presented than when inverted hand or arrow images were presented. However, this effect was not observed for the TOJ between an auditory stimulus and a visual stimulus. Thus, the visual presentation of a hand image whose angle corresponds to that of one’s own hand could selectively degrade visuo–tactile TOJ. This finding indicates that visual hand images implicitly enhance the internal proximity between the visual and tactile stimuli and make them difficult to distinguish from each other in the temporal domain.     

Characteristics of activation in the parietal areas of the cortex in humans in different types of visual attention

The state of cortical activation in the parietal and temporal areas was assessed using evoked potentials (EP) during the tasks of selection of lateralized visual stimuli requiring three different types of attention: to stimulus shape, to stimulus position, and to both. Studies in 15 young, healthy subjects involved recording of EP in six cortical leads: P3, P4, T3, T4, T5, and T6, with analysis of the endogenous EP components CNV, N1, P3, and the EP complex [N1-P3] (according to standard terminology). Changes in EP components in response to the attended and non-attended stimulus features were compared. Differences between them were assessed using the index of selectivity of attention to one or another feature of the visual stimuli. In the parietal area, selectivity was seen in conditions of attention to stimulus position and attention to stimulus shape. In conditions of simultaneous attention, the indexes of selectivity were essentially equal to the sum of the indexes of selectivity of attention to shape and position. The most marked endogenous EP components (CNV, N1, and P3) in visual selection were seen in the parietal areas, with a greater gradient of increased activation of the parietal areas of the cortex as the need for attention increased, along with a lower threshold for the action of attention, and anticipatory development of the P3 wave in the parietal area as compared with the temporal area. These results suggest that the parietal cortex has priority in the visual attention system and that the magnocellular (M) pathway forms the most important visual input to the dorsal parietal area of the neocortex. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 92, No. 2, pp. 178–190, February, 2006.     

Visually cued motor synchronization: modulation of fMRI activation patterns by baseline condition

A well-known issue in functional neuroimaging studies, regarding motor synchronization, is to design suitable control tasks able to discriminate between the brain structures involved in primary time-keeper functions and those related to other processes such as attentional effort. The aim of this work was to investigate how the predictability of stimulus onsets in the baseline condition modulates the activity in brain structures related to processes involved in time-keeper functions during the performance of a visually cued motor synchronization task (VM). The rational behind this choice derives from the notion that using different stimulus predictability can vary the subject's attention and the consequently neural activity. For this purpose, baseline levels of BOLD activity were obtained from 12 subjects during a conventional-baseline condition: maintained fixation of the visual rhythmic stimuli presented in the VM task, and a random-baseline condition: maintained fixation of visual stimuli occurring randomly. fMRI analysis demonstrated that while brain areas with a documented role in basic time processing are detected independent of the baseline condition (right cerebellum, bilateral putamen, left thalamus, left superior temporal gyrus, left sensorimotor cortex, left dorsal premotor cortex and supplementary motor area), the ventral premotor cortex, caudate nucleus, insula and inferior frontal gyrus exhibited a baseline-dependent activation. We conclude that maintained fixation of unpredictable visual stimuli can be employed in order to reduce or eliminate neural activity related to attentional components present in the synchronization task.     

酗酒者皮层脑电同步性分析

同步性可以度量不同脑区之间的相互作用,但目前对脑电的同步性研究多数是基于头皮数据进行的。脑电的容积导体效应,可能导致头皮电极之间出现伪相关,从而影响同步性的度量。实验所用的数据集包括正常(28例)和酗酒(28例)两类被试的61通道EEG时间序列,每一个被试参与3种条件的实验任务:单刺激(S1)、双刺激匹配(S2 match)、双刺激不匹配(S2 no match)。利用eLoreta溯源技术,在大脑皮层上自定义了61个感兴趣区域(ROI),计算两类被试之间的同步似然性,最后对酗酒被试和正常被试执行认知任务时的同步性差异进行统计分析。结果发现,执行相同认知任务时,酗酒被试全脑平均同步似然均小于正常被试,且在α、β1和θ波段上均有P<0.05,差异达到统计显著。在执行不同认知任务时,正常被试的同步性可以准确反映出不同认知任务的复杂程度(S2 match > S2 no match > S1),而酗酒被试的同步性则无规律变化。不同被试之间的区域MSL结果表明,在执行S2 match任务时,酗酒被试多个区域MSL均小于正常被试,且在α波段上额叶、左颞叶、中央和右颞叶区均有P<0.05,差异达到统计显著;在β1波段上,额叶区P<0.05,差异达到统计显著;在β2波段上,额叶、左颞叶区均有P<0.05,差异达到统计显著。研究结果表明,酗酒被试大脑不同区域之间的连接受到一定程度的损伤,这为研究酗酒引起的脑损伤提供一个新的角度和有力的证据。     

Contextual modulation of synchronization to random dots in the cat visual cortex

Synchronization of neuronal activity has been proposed as a binding mechanism for integration of image properties into one coherent percept. In the present study, we investigated the contextual modulation of synchronization to random dot patterns. Coherent motion of random dots evoked well synchronized responses in area 17 of anaesthetized cats when the stimulus was presented in the compound receptive field of recorded sites. Gradually changing the directional coherence of random dots in the surround while maintaining fully coherent motion of the stimulus in the receptive field significantly suppressed synchronization of neuronal activity for some stimulus conditions. However, usually one or two peaks of increased synchronization were found in the surround coherence tuning curves with low (8–12%) and/or moderate (25–50%) coherence in the surround. At the population level, synchronization was significantly depressed with incoherent motion in the receptive field and when both the surround and the receptive field were jointly stimulated with 0% coherence. The intriguing finding was the discovery of two distinct groups of cells with opposite synchronization changes dependent on the presence or absence of significant synchronization in their spontaneous activity. The latter group of neurons showed peaks of increased synchronization with lower surround coherence, thus probably being more sensitive to the direction of the surround motion. Overall, our findings support the notion that binding of stimulus properties can be achieved by synchronized activity of cortical cells. However, our findings go further than the original hypothesis of feature binding by synchrony to show that synchronization of cortical activity may be directly related to the decision making processes, which in turn are related to the threshold of perception of coherent motion.     

Stimulus repetition affects both strength and synchrony of macaque inferior temporal cortical activity

Repetition of a visual stimulus reduces the firing rate of macaque inferior temporal (IT) neurons. The neural mechanisms underlying this adaptation or repetition suppression are still unclear. In particular, we do not know how the IT circuit is affected by stimulus repetition. To address this, we measured local field potentials (LFPs) and multiunit spiking activity (MUA) simultaneously at 16 sites with a laminar electrode in IT while repeating visual images. Stimulus exposures and interstimulus intervals were each 500 ms. The rhesus monkeys were performing a passive fixation task during the recordings. Induced LFP power decreased with repetition for spectral frequencies above 60 Hz but increased with repetition for lower frequencies, the latter because of a delayed decrease in power when repeating a stimulus. LFP-LFP and MUA-LFP coherences decreased with repetition for frequencies above 60 Hz. This repetition suppression of the MUA-LFP coherence was not due to differences in firing rate since it was present when spike counts were equated for the adapter and repeated stimuli. For frequencies between 15 and 40 Hz, the effect of repetition on synchronization depended on the electrode depth: For the putative superficial layers synchronization was enhanced with repetition, while the LFPs of the putative deep layers decreased their synchrony across layers. The between-site, trial-to-trial covariations in MUA ("noise correlations") decreased with repetition, but this might have reflected repetition suppression of the firing rate. This work demonstrates that short-term stimulus repetition affects the synchronized activity, in addition to response strength, in IT cortex.     

Cortical activity related to cue-invariant shape perception in humans

We used magnetoencephalography to search spatio-temporally for cortical activity related to the perception of shape defined by various visual cues in humans. The visual stimuli were three kinds of two-dimensional figures: two had fixed shapes (Diamond and Cross), the other did not (Noise). These figures were defined by three visual cues: difference of flicker, texture or luminance between the foreground and the background in the random dot pattern. Using this stimulus, we recorded the magnetic responses from the temporo-occipital regions of nine healthy subjects. Additionally, we measured the reaction time for the subjects to detect the figure by button-pressing. A magnetic component was identified in the responses. The properties of the first magnetic component differed for stimulus condition. The peak latency of the first magnetic component was different for the cues (270 ms for flicker, 360 ms for texture and 250 ms for luminance), but not for the figures. In contrast, the peak amplitude of the first magnetic component was different for the figures (96-144 fT for Diamond or Cross and 52-80 fT for Noise), but not for the cues. The signal source of the first magnetic component was estimated to lie on the ventral side of the extrastriate cortex: In the posterior part of the inferior temporal cortex, probably in the fusiform gyrus in four subjects, and in the lateral part of the occipital cortex which was outside of the primary visual cortex (visual area 1) in one subject. The signal source location was different inter-individually, but almost the same within each subject. Reaction time was 471 ms for flicker, 569 ms for texture and 426 ms for luminance, but the interval between the reaction time and the peak latency was constant (about 200 ms) for each cue. The first magnetic component was more clearly recorded from the right hemisphere than from the left.We found that the shape defined by the different visual cues activates the same localized site in the lateral extrastriate cortex. This spatial convergence suggests that there is a restricted locus that processes the visual shape regardless of the difference of the visual cue. The correspondence between the peak latency and the reaction time suggests that the activity of the area is responsible for the perception of visual shape. The inter-hemispheric difference suggests a dominance of the right hemisphere in visual shape processing.     

Early induced beta/gamma activity during illusory contour perception

The temporal binding hypothesis proposes that visual feature binding is achieved by neuronal synchronization. Nevertheless, the existing human neurophysiological evidence for the neuronal synchronization in visual feature binding—the oscillatory induced beta/gamma activity (IB/GA) is under suspicion. The previously observed IB/GA occurs at a later stage (after 200 ms), thus leading to the objection that IB/GA may be related to some later top-down processes rather than the early perceptual processing. However, the present EEG study identified an IB/GA as early as 90 ms after stimulus onset, which was stronger for a Kanizsa-type illusory contour (IC, a classic example of visual feature binding) than for a control stimulus. This finding provides new human evidence for the temporal binding hypothesis that neuronal synchronization occurs at the early stage of visual feature binding.